The present invention relates to a securing structure and a securing unit for securing a measuring member, which has a sensor element and a lead elongated from the sensor element, to a subject to be measured, in particular to a securing structure and a securing unit suitable for securing a thermistor to a reactor.
In general, a reactor has, for example, a winding and a core made of a magnetic substance and the winding is wound around the core to make up the coil of the reactor, which enables inductance to be obtained. Conventionally, the reactor is used in a voltage boosting circuit, inverter circuit, active filter circuit, or the like, and, in many cases, such the reactor has a structure in which the core and the coil wound around the core are housed, together with other insulating members or the like in a case made of metal or the like. Japanese Patent Application Laid-open No. 2003-124039 discloses an example of such a reactor.
For a reactor to be used in a vehicle-mounted voltage boosting circuit, a coil is used which has a structure in which two single-coil elements each having a predetermined winding diameter and the number of windings that can provide a high inductance value in a high current region are formed in parallel to each other and are coupled (connected) to each other so that the directions of currents flowing through both the coils are reversed to one another. If high current has been continuously applied to a reactor thus mentioned, the coil comes to be overheated and an electric characteristic of the reactor is thereby deteriorated. Under the circumstances, an internal temperature of the reactor is measured using a sensor such as a thermistor, or the like. The reactor is thereby controlled so as to prevent the coil from generating heat up to a certain temperature or a higher temperatures thereof. Namely, the measuring member, which has the sensor element and the lead elongated from the sensor element, is secured within the reactor in order that the sensor element, such as a thermistor, or the like, may be positioned at a measured point near the coil within the reactor, that is the subject member to be measured. Thereby, the internal temperature of the reactor is measured, so that a current flowing in the reactor is controlled to prevent the coil from generating heat up to the certain temperature or the higher temperatures thereof.
In order to stably fabricate reactors having the sensor elements, such as thermistors, or the like each capable of measuring temperature with high precision, it is necessary that the sensor elements are positioned at the same points within the reactors, respectively. However, it is almost impossible that the sensor element connected to a head portion of a lead is directly secured at the measured point within each reactor. Therefore, another portion of the lead other than the head portion thereof is secured at a portion of a reactor case with a screw. Under the circumstances, it is difficult that the sensor elements are precisely positioned at the same points within the reactors, respectively. Further, it becomes necessary to provide a securing structure with the screw in the another portion of the lead other than the head portion thereof. This causes a much cost up of members for measuring temperature of the reactor.
However, in fact, no effective proposal has been made about a technique for precisely positioning and securing the sensor element connected to the head portion of the lead within the reactor in spite of a compact configuration by the no use of the securing structure with the screw thus mentioned.
Accordingly, it is desired to develop a non-complicated and effective securing structure suitable for various subjects to be measured. In particular, it is strongly desired to develop such a non-complicated and effective securing structure suitable for a compact and thin-sized reactor that has come to be often used in a reactor mounted on an automobile in recent years.